#include <stdio.h>
#include <stdlib.h>

int main()
{
    float   acconts = 0.0;
    float   f = 0.0;
    int i = 0;

    for(i = 0; i < 12; i++)
    {
        scanf("%f", &f);
        acconts += f;
    }

    printf("$%.2f\n", acconts / 12);
    return 0;
}